1. Field of the Invention
The present invention is related to a method for recording wobble information of an information recording medium such as an optical disk so that a polarity of detected wobble information is the same irrespective of the recording system, and an information recording medium wherein the wobble information is recorded according to the method. Further, the present invention is related to a method and apparatus for recording and reproducing information using the information recording medium.
2. Description of the Related Art
Conventionally, CD-R/RW and DVD-R/RW/RAM have been used as a write-once or a rewritable optical disk and recently demand for a DVD-R/RW/RAM has been increased since DVD recorders have widely prevailed for recording TV broadcasts. A guide groove is provided in these optical disks and reference signals for synchronizing a linear velocity upon recording and reproducing and optional address information signals are recorded in these optical disks by “wobble” signals which are a meander of the guide groove. A recording and reproduction apparatus for such an optical disk records and reproduces information by detecting the wobble signals to adjust the linear velocity and by detecting the address if the address information is added to the optical disk. Of the above optical disks, the DVD-RAM employs a recording system (or a recording mode) which may be called as a “land & groove” recording system according to which recording and reproduction of information are carried out on both land portions (that are faces far from a light used for recording and reproduction) and the groove portions (that are faces near to the light) of the guide groove, and all the other optical disks employ a groove recording system according to which the recording and reproduction of information are carried out only on the groove portions (that are faces near to the light used for recording and reproduction) of the guide groove.
Recently, an optical disk having a recording density that is higher than the DVD has been developed. In general, information is recorded on and reproduced from the optical disk by an incident light for recording and reproduction which light passes through a transparent layer which may be called a “substrate.” The thickness of the substrate, through which the light for recording and reproduction passes, is 0.6 mm for the DVD. A study has been made for further thinning the thickness of the substrate into about 0.1 mm and thereby using a light with a short wavelength for recording and reproduction. As a result, a recordable Blu-ray Disc (BD) has been developed.
In the case where the thickness of the substrate is thin such as 0.1 mm, it is difficult to form the guide groove in the sheet having a thickness of 0.1 mm and to form the recording layer on its surface. For this reason, an approach for producing the Blu-ray Disc is made wherein the guide groove is formed in a substrate of a 1.1 mm thickness which is to be positioned at the side (rear side) that is not irradiated with the light for recording and reproducing and the recording layer is formed on the guide groove followed by forming a cover layer of a 0.1 mm thickness. In this case, the light for recording and reproducing is applied from the side of the cover layer.
When the recording layer is formed by sputtering a material forming the recording layer onto the surface of the rear-side substrate, the recording layer can be deposited and formed so that the thickness of the recording layer in the groove portions (the top surface of the guide groove) is almost the same as that in the land portions (the bottom surface of the guide groove) viewed from the cover layer side where the light for recording and reproducing is applied. Therefore, in this case, the portions that present better recording and reproduction characteristics, which is generally the groove portions, can be used for recording and reproduction.
Further, there is a method for applying an organic dye by a spin-coat method, as a method for forming the recording layer. For example, Japanese Patent Kokai (Laid-Open) Publication No. 2003-109246(A) describes a method for producing a write-once optical disk which includes forming the recording layer by applying the organic dye on the rear-side substrate by the spin-coat method and then forming the cover layer. However, according to the spin coat method, the organic dye preferentially deposits in the groove portions (concaved portions) of the substrate. As a result, the recording layer is formed thickly in the land portions when viewed from the cover layer side. Therefore, since the recording film is easily formed in the land portions in this case, it is preferable that the land portions are used for recording and reproduction.